1. Field of the Invention
This invention concerns a heat exchanger structure in general and, more particularly, it is applicable to synthesis gas cooling in a waste heat boiler structure.
2. Description of the Prior Art
While there are various waste heat boiler structures employed in different environments and for different applications, the cooling of hot synthesis gas from a gasifier handling finely divided solids, e.g. powdered coal, has heretofore employed a radiation boiler which raises steam in water wall tubes. With such a boiler, the solidified slag and cooled synthesis gas are removed at the bottom of a downflow radiation boiler. However, in commercial sized plants the radiation boiler dimensions would become a limiting factor where a single train throughput flow of the hot synthesis gas is employed.
Furthermore, while heretofore there have been various structures for waste heat boilers used for transferring heat from the flow of hot gases that are to be cooled, they would not be adaptable for large scale flow of synthesis gas. Also, while there is a known waste heat boiler that has a complex structure, i.e. that described in U.S. Pat. No. 3,628,508 to Kummel issued Dec. 21, 1971, it would be costly to make and would not be feasible for use with the high temperatures involved in synthesis gas cooling. Also, there is no known structure for having radiant transfer of hot synthesis gas flowing axially through the boiler with reversal into an annulus along with a quenching bath for removing entrained solids.
Consequently, it is an object of this invention to provide a synthesis gas cooler structure that is applicable to a waste heat boiler element for heat recovery. It employs direct downward flow for radiant heat transfer, with reversal and quenching of entrained solids prior to return flow in an annular space which leads to an outlet for the cooled synthesis gas.